1. Field of the Invention
The present invention relates to a device monitoring apparatus that monitors devices on a network such as a copier and a printer, a control method for the device monitoring apparatus, a device monitoring system that includes the device monitoring apparatus, and a recording medium that stores a program for realizing the control method.
2. Description of the Related Art
Conventionally, a system has generally been known that monitors a change in the state of devices such as a copier and a printer on a network. A system of this type includes a monitoring device that performs monitoring (hereinafter referred to as the master unit). The master unit transmits to devices as monitored objects (hereinafter referred to as the slave units) on the network a request for acquisition of information at regular intervals of time in order to inspect the states of the slave units. In a case for example that the slave unit is a copier, when a request for acquisition of information on operation state, setting information on toner amount, sheet feed cassette, etc., error information on print sheet jam, out of print sheets, etc., is transmitted from the master unit, the slave unit sends the requested information back to the master unit.
Thus, the master unit grasps the state of the slave unit. When, for example, an error occurs in the slave unit to be monitored, the master unit transmits an e-mail to a manager or displays a notification on a monitor, whereby the device monitoring is achieved.
In the above monitoring system, after the slave unit shifts into a sleep state (a mode the slave unit enters when not operated for a given time period or more) or into a power-off state, the state of the slave unit does not change and therefore the monitoring is no longer necessary. In that case, it is preferable to properly control power supply to a system controller of the master unit that performs the device monitoring, in order to reduce power consumption.
To this end, there has conventionally been proposed a technique in which the master unit stops transmitting the information acquisition request for the device monitoring in response to a notification of transition to the sleep state being transmitted from the slave unit, and resumes the device monitoring when the slave unit returns from the sleep state (see, for example, Japanese Laid-open Patent Publication No. 2000-103148). Also proposed is a technique in which the interval at which the information acquisition request is transmitted for the device monitoring is made longer in accordance with the state of the slave unit (see, for example, Japanese Laid-open Patent Publication No. 2006-215686), thereby reducing load on the master unit and achieving a reduction in power consumption.
However, with the technique disclosed in Japanese Laid-open Patent Publication No. 2000-103148, the master unit cannot stop transmitting the information acquisition request in a case where the slave unit is not provided with means for notifying the return from the sleep state. Usually, after the slave unit shifts into the sleep state or the power-off state, the slave unit does not respond to the information acquisition request from the master unit. In that case, the master unit cannot detect on the network that the slave unit returns from the sleep state or shifts into the power-on state. Therefore, in order to monitor a change in the state of the slave unit (returning from the sleep state or turning-on of power), the master unit must transmit the information acquisition request even when the slave unit is in the sleep state or in the power-off state.
With the technique disclosed in Japanese Laid-open Patent Publication No. 2006-215686, even if the interval at which the information acquisition request is transmitted for monitoring the slave unit is made longer, a large load is applied to the master unit at intervals of a given time period in the case of large-scaled master unit, resulting in a problem that the power consumption for the monitoring cannot effectively be reduced.